Update returning for Slick 3.1.1

UpdateReturning.scala

private def updateReturning[A, F](
    returningQuery: Query[A, F, C], v: U): SqlStreamingAction[Vector[F], F, Effect.All] = {
  val ResultSetMapping(
  _, CompiledStatement(_, sres: SQLBuilder.Result, _), CompiledMapping(_updateConverter, _)) =
    updateCompiler.run(updateQuery.toNode).tree

  val pconv: SetParameter[U] = {
    val ResultSetMapping(_, compiled, CompiledMapping(_converter, _)) =
      updateCompiler.run(updateQuery.toNode).tree
    val converter = _converter.asInstanceOf[ResultConverter[JdbcResultConverterDomain, U]]
    SetParameter[U] { (value, params) ⇒
      converter.set(value, params.ps)
    }
  }

  // extract the result/converter to build our RETURNING {columns} and re-use it for result conversion
  val ResultSetMapping(_,
                       CompiledStatement(_, returningResult: SQLBuilder.Result, _),
                       CompiledMapping(resultConverter, _)) =
    queryCompiler.run(returningQuery.toNode).tree

  val rconv: GetResult[F] = {
    val converter = resultConverter.asInstanceOf[ResultConverter[JdbcResultConverterDomain, F]]
    GetResult[F] { p ⇒
      converter.read(p.rs)
    }
  }

  // extract columns from the `SELECT {columns} FROM {table}` after dropping `FROM .*` from query str
  val columns      = columnRegex.findAllIn(returningResult.sql.replaceAll(" from .*", "")).toList
  val fieldsExp    = columns.mkString(", ")
  val returningSql = sres.sql + s" RETURNING $fieldsExp"

  SQLActionBuilder(returningSql, pconv.applied(v)).as[F](rconv)
}

This code is incomplete. columnRegex is not defined.

val columnRegex: Regex = "(\".*\")".r